Apparatus for effecting such transfer operations is already known e.g. from U.S. Pat. No. 3,949,891 filed July 22nd 1974 and entitled "Semi Conductor Wafer Transfer Device" but, irrespective of whether they are manually or automatically operated, they suffer from the disadvantage that the transfer was affected by bringing the two carrier members into an inverted position in register and the two devices were turned over, together. Therefore the wafers fell a distance roughly equal to the added depths of both carrier members; this may lead to cracking or chipping of wafer edges and lead to frequent rejection of the wafers.